Supramolecular chemistry provides tools for the assembly and actuation of molecular systems. The reversibility of association of host-guest systems enables facile assembly and disassembly coupled with 'lock and key' specificity. In our proposed research we will develop new therapeutics based on intracellular host-guest actuation of nanoparticle protherapeutics. This approach provides a new strategy for the creation of bioactive materials that will enable multiple targeting strategies inaccessible with current systems. In our proposed research, we will develop new nanoparticle protherapeutics based on nanoparticle-cucurbituril (CB) host-guest complexes. These complexes dissociate inside the cell in the presence of competitive binders for CB, unmasking and activating the cytotoxic particle therapeutic. This intracellular actuation process will be quantified using mass spectrometric techniques. We will then use the unique intracellular actuation process to enable new targeting approaches, including dual-targeting strategies that are expected to be highly specific to cells overexpressing multiple receptors.